This work presents an experimental study of the gasification of a wood biomass in a moving bed downdraft reactor with two-air supply stages. This configuration is considered as primary method to improve the quality of the producer gas, regarding its tar reduction. By varying the air flow fed to the gasifier and the distribution of gasification air between stages (AR), being the controllable and measurable variables for this type of gasifiers, measuring the CO, CH4 and H2 gas concentrations and through a mass and energy balance, the gas yield and its power, the cold efficiency of the process and the equivalence ratio (ER), as well as other performance variables were calculated. The gasifier produces a combustible gas with a CO, CH4 and H2 concentrations of 19.04, 0.89 and 16.78% v respectively, at a total flow of air of 20 Nm3 h-1 and an AR of 80%. For these conditions, the low heating value of the gas was 4539 kJ Nm-3. Results from the calculation model show a useful gas power and cold efficiency around 40 kW and 68%, respectively. The resulting ER under the referred operation condition is around 0.40. The results suggested a considerable effect of the secondary stage over the reduction of the CH4 concentration which is associated with the decreases of the tar content in the produced gas. Under these conditions the biomass devolatilization in the pyrolysis zone gives much lighter compounds which are more easily cracked when the gas stream passes through the combustion zone.
Bibliographical noteFunding Information:
The authors would like to express their gratitude to Companhia Paulista de Força e Luz (CPFL) and the National Research Council of Brazil (CNPq) for the financial support received for this project development. Also we would like to thank the Committee on Coordination of Improvements in Higher Education (CAPES), CNPq and the Foundation of Science Support from the State of Minas Gerais (FAPEMIG) for graduate and research productivity grants allocations. Furthermore, we would like to acknowledge the company Termoquip Energia Alternativa Ltda and UFPa for the biomass characterization.
- Double stage gasification
- Downdraft reactor
- Producer gas